Physiological acoustic monitoring system

ABSTRACT

An acoustic monitoring system has an acoustic front-end, a first signal path from the acoustic front-end directly to an audio transducer and a second signal path from the acoustic front-end to an acoustic data processor via an analog-to-digital converter. The acoustic front-end receives an acoustic sensor signal responsive to body sounds in a person. The audio transducer provides continuous audio of the body sounds. The acoustic data processor provides audio of the body sounds upon user demand.

This application is a continuation of Ser. No. 14/473,831, filed Aug.29, 2014, which is a divisional of U.S. patent application Ser. No.12/905,036, filed Oct. 14, 2010, now U.S. Pat. No. 8,821,415, whichclaims the benefit of priority under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 61/252,099, filed Oct. 15, 2009, and U.S.Provisional No. 61/391,098, filed Oct. 8, 2010, the disclosures of eachof which are incorporated in their entirety by reference herein.

Additionally, this application relates to the following U.S. patentapplications, the disclosures of which are incorporated in theirentirety by reference herein:

application Filing Ser. No. Date Title 60/893,853 Mar. 8, 2007MULTI-PARAMETER PHYSIOLOGICAL MONITOR 60/893,850 Mar. 8, 2007 BACKWARDCOMPATIBLE PHYSIOLOGICAL SENSOR WITH INFORMATION ELEMENT 60/893,858 Mar.8, 2007 MULTI-PARAMETER SENSOR FOR PHYSIOLOGICAL MONITORING 60/893,856Mar. 8, 2007 PHYSIOLOGICAL MONITOR WITH FAST GAIN ADJUST DATAACQUISITION 12/044,883 Mar. 8, 2008 SYSTEMS AND METHODS FOR DETERMININGA PHYSIOLOGICAL CONDITION USING AN ACOUSTIC MONITOR 61/252,083 Oct. 15,2009 DISPLAYING PHYSIOLOGICAL INFORMATION 12/904,836 Oct. 14, 2010BIDIRECTIONAL PHYSIOLOGICAL INFORMATION DISPLAY 12/904,823 Oct. 14, 2010BIDIRECTIONAL PHYSIOLOGICAL INFORMATION DISPLAY 61/141,584 Dec. 30, 2008ACOUSTIC SENSOR ASSEMBLY 61/252,076 Oct. 15, 2009 ACOUSTIC SENSORASSEMBLY 12/643,939 Dec. 21, 2009 ACOUSTIC SENSOR ASSEMBLY 61/313,645Mar. 12, 2010 ACOUSTIC RESPIRATORY MONITORING SENSOR HAVING MULTIPLESENSING ELEMENTS 12/904,931 Oct. 14, 2010 ACOUSTIC RESPIRATORYMONITORING SENSOR HAVING MULTIPLE SENSING ELEMENTS 12/904,890 Oct. 14,2010 ACOUSTIC RESPIRATORY MONITORING SENSOR HAVING MULTIPLE SENSINGELEMENTS 12/904,938 Oct. 14, 2010 ACOUSTIC RESPIRATORY MONITORING SENSORHAVING MULTIPLE SENSING ELEMENTS 12/904,907 Oct. 14, 2010 ACOUSTICPATIENT SENSOR 12/904,789 Oct. 14, 2010 ACOUSTIC RESPIRATORY MONITORINGSYSTEMS AND METHODS 61/252,062 Oct. 15, 2009 PULSE OXIMETRY SYSTEM WITHLOW NOISE CABLE HUB 61/265,730 Dec. 1, 2009 PULSE OXIMETRY SYSTEM WITHACOUSTIC SENSOR 12/904,775 Oct. 14, 2010 PULSE OXIMETRY SYSTEM WITH LOWNOISE CABLE HUB 61/331,087 May 4, 2010 ACOUSTIC RESPIRATION DISPLAY

Many of the embodiments described herein are compatible with embodimentsdescribed in the above related applications. Moreover, some or all ofthe features described herein can be used or otherwise combined withmany of the features described in the applications listed above.

BACKGROUND

The “piezoelectric effect” is the appearance of an electric potentialand current across certain faces of a crystal when it is subjected tomechanical stresses. Due to their capacity to convert mechanicaldeformation into an electric voltage, piezoelectric crystals have beenbroadly used in devices such as transducers, strain gauges andmicrophones. However, before the crystals can be used in many of theseapplications they must be rendered into a form which suits therequirements of the application. In many applications, especially thoseinvolving the conversion of acoustic waves into a corresponding electricsignal, piezoelectric membranes have been used.

Piezoelectric membranes are typically manufactured from polyvinylidenefluoride plastic film. The film is endowed with piezoelectric propertiesby stretching the plastic while it is placed under a high-polingvoltage. By stretching the film, the film is polarized and the molecularstructure of the plastic aligned. A thin layer of conductive metal(typically nickel-copper) is deposited on each side of the film to formelectrode coatings to which connectors can be attached.

Piezoelectric membranes have a number of attributes that make theminteresting for use in sound detection, including: a wide frequencyrange of between 0.001 Hz to 1 GHz; a low acoustical impedance close towater and human tissue; a high dielectric strength; a good mechanicalstrength; and piezoelectric membranes are moisture resistant and inertto many chemicals.

Due in large part to the above attributes, piezoelectric membranes areparticularly suited for the capture of acoustic waves and the conversionthereof into electric signals and, accordingly, have found applicationin the detection of body sounds. However, there is still a need for areliable acoustic sensor, particularly one suited for measuring bodilysounds in noisy environments.

SUMMARY

An aspect of an acoustic monitoring system has an acoustic front-end, afirst signal path from the acoustic front-end directly to an audiotransducer and a second signal path from the acoustic front-end to anacoustic data processor via an analog-to-digital converter. The acousticfront-end receives an acoustic sensor signal responsive to body soundsin a person. The audio transducer provides continuous audio of the bodysounds. The acoustic data processor provides audio of the body soundsupon user demand.

In various embodiments, a second acoustic front-end receives a secondacoustic sensor signal responsive to body sounds in a person. A thirdsignal path is from the second acoustic front-end to a parameterprocessor via the analog-to-digital converter. The parameter processorderives a physiological measurement responsive to the body sounds. Afourth signal path is from the second acoustic front-end to the acousticdata processor via the analog-to-digital converter. The acoustic dataprocessor provides a stereo audio output of the body sounds.

In other embodiments, the acoustic monitoring system further comprises acommunications link to a remote site via a network. A trigger isresponsive to the physiological measurement. A notification istransmitted over the communications link according to the trigger. Thenotification alerts an individual at the remote site of thephysiological measurement and allows the individual to request the bodysounds be downloaded to the individual via the communications link. Anoptical front-end receives an optical signal responsive to pulsatileblood flow at a tissue site on the person. The parameter processorderives a second physiological measurement responsive to the pulsatileblood flow. The trigger is responsive to a combination of thephysiological measurement and the second physiological measurement.

Further embodiments comprise acoustic filters implemented in theacoustic data processor. The filters define a series of audiobandwidths. Controls are in communications with the acoustic dataprocessor. The controls are configured to adjust the audio bandwidths.The stereo audio output is adjusted by the controls so as to emphasizeat least one of the audio bandwidths and deemphasize at least one otherof the audio bandwidths so that a user of the controls can focus on aparticular aspect of the stereo body sound output. The acousticmonitoring system further comprises a display that is responsive inreal-time to the stereo audio output.

Another aspect of an acoustic monitoring system inputs a sensor signalresponsive to body sounds of a living being. The sensor signal routes toan audio output device so as to enable a first user to listen to thebody sounds. The sensor signal is digitized as acoustic data, and theacoustic data is transmitted to a remote device over a network. Theacoustic data is reproduced on the remote device as audio so as toenable a second user to listen to the body sounds.

In various embodiments, the acoustic data is transmitted when a requestis received from the remote device to transmit the body sounds. Therequest is generated in response to the second user actuating a buttonon the remote device to listen-on-demand. Further, a physiological eventis detected in the sensor signal and a notification is sent to thesecond user in response to the detected event. The acoustic datatransmission comprises an envelope extracted from the acoustic data anda breath tag sent to the remote device that is representative of theenvelope.

In other embodiments, the reproduced acoustic data comprises thesynthesized envelope at the remote device in response to the breath tag,where the envelope is filled with white noise. The reproduced acousticdata may also comprise the envelope modified with a physiologicalfeature derived from the breath tag. The acoustic data may be stored ona mass storage device as a virtual tape. A searchable feature of thecontents of the virtual tape in logged in a database and the virtualtape is retrieved from the mass storage device according to thesearchable feature.

A further aspect of an acoustic monitoring system has an acousticsensor, a sensor interface and a wireless communications devicecomprising a first monitor section. The acoustic sensor has apiezoelectric assembly, an attachment assembly and a sensor cable. Theattachment assembly retains the piezoelectric assembly and one end ofthe sensor cable. The attachment assembly has an adhesive so as toremovably attach the piezoelectric assembly to a tissue site. The otherend of the sensor cable is communications with a sensor interface so asto activate the piezoelectric assembly to be responsive to body soundstransmitted via the tissue site. The wireless communications device isresponsive to the sensor interface so as to transmit the body soundsremotely.

The acoustic monitor has a second wireless communications device and anaudio output device comprising a second monitor section. The secondwireless communications device is responsive to the wirelesscommunications device so as to receive the body sounds. The audio outputdevice is responsive to the second wireless communications device so asto audibly and continuously reproduce the body sounds.

The first monitor section is located near a living person and the secondwireless communications device is located remote from the living personand attended to by a user. The sensor is adhesively attached to theliving person so that the user hears the body sounds from the livingperson via the sensor and a continuous audio output. In an embodiment,the first monitor section is located proximate to an infant, the sensoris adhesively attached to the infant, the second monitor section islocated remote to the infant proximate the adult and the continuousaudio output allows the adult to monitor the infant so as to avoidsudden infant death syndrome (SIDS).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general block diagram of a physiological acoustic monitoringsystem;

FIGS. 2A-B are illustrations of dual channel acoustic sensors;

FIG. 2A illustrates a neck sensor for physiological measurements and achest sensor for monaural body sound monitoring;

FIG. 2B illustrates a dual acoustic sensor for stereo body soundmonitoring;

FIGS. 3A-B are top and bottom perspective views of a body sound sensor;

FIG. 4 is a general schematic diagram of acoustic and optic sensor driveelements;

FIG. 5 is a general schematic diagram of a physiological acousticmonitor and corresponding sensor interface elements;

FIG. 6 is a network diagram for a physiological acoustic monitoringsystem;

FIGS. 7A-B are block diagrams illustrating an acoustic-envelope-basedbreath sound generator;

FIGS. 8A-C are graphs of illustrating an acoustic-envelope-based breathsound generator; and

FIG. 9 is an illustration of a physiological acoustic monitoring systemfor out-patient monitoring applications.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 generally illustrates a physiological acoustic monitoring system100 embodiment having one or more sensors 110 in communications with oneor more processors 130 via a sensor interface 120. The processors 130both initiate and respond to input/output 150, including audio output152, displays and alarms 154, communications 156 and controls 158. In anembodiment, the processors 130 are implemented in firmware executing onone or more digital signal processors (DSP), as described with respectto FIGS. 5-6, below. At least a portion of the sensors 110 generateacoustic signals, which may be directly utilized by the processors 130or recorded onto or played back from storage media 160 or both.

The processors 130 include an audio processor 132 that outputs audiowaveforms 142, a parameter processor 134 that derives physiologicalparameters 144 from sensor signals 112 and an acoustic data processor136 that stores, retrieves and communicates acoustic data 146.Parameters include, as examples, respiration rate, heart rate and pulserate. Audio waveforms include body sounds from the heart, lungs,gastrointestinal system and other organs. These body sounds may includetracheal air flow, heart beats and pulsatile blood flow, to name a few.Displays allow parameters 144 and acoustic data 146 to be visuallypresented to a user in various forms such as numbers, waveforms andgraphs, as examples. Audio 152 allows audio waveforms to be reproducedthrough speakers, headphones or similar transducers. Raw audio 122allows acoustic sensor signals 112 to be continuously reproduced throughspeakers, headphones or similar transducers, bypassing A/D conversion120 and digital signal processing 130.

Storage media 160 allows acoustic data 146 to be recorded, organized,searched, retrieved and played back via the processors 130,communications 156 and audio output 152. Communications 156 transmit orreceive acoustic data or audio waveforms via local area or wide areadata networks or cellular networks 176. Controls 158 may cause the audioprocessor 132 to amplify, filter, shape or otherwise process audiowaveforms 142 so as to emphasize, isolate, deemphasize or otherwisemodify various features of an audio waveform or spectrum. In addition,controls 158 include buttons and switches 178, such as a “push to play”button that initiates local audio output 152 or remote transmission 176of live or recorded acoustic waveforms.

As shown in FIG. 1, acoustic data 146 is initially derived from one ormore acoustic sensor signals 112, along with, perhaps, other datainputs, such as from optical, blood pressure, EEG and ECG sensors, toname a few. The acoustic data 146 provides audio outputs 142, includingaudio respiration indicators, described with respect to FIGS. 8-9,below. The acoustic data 146, when analyzed, provides physiologicalparameters 144 that provide an indication of patient status, such asrespiration rate or heart rate. Such analyses may result in visual oraudible alerts or alarms 154 that are viewed locally or vianotifications transmitted over local or wide area networks 176 tomedical staff or other persons. Acoustic data 146 is utilized in realtime or stored and retrieved for later use. Acoustic data 146 may bewritten on various storage media 160, such as a hard drive, andorganized for convenient search and retrieval. In an embodiment,acoustic data 146 is advantageous organized on one or more hard drivesas virtual magnetic tape so as to more easily manage, search, retrieveand playback acoustic data volumes. Further, the virtual tape volumesand/or the acoustic data itself may be entered into a database andorganized as an acoustic library according to various search parametersincluding patient information, dates, corresponding physiologicalparameters and acoustic waveform features, to name a few. Applicationsfor a physiological acoustic monitoring system include auscultation ofbody sounds by medical staff or by audio processors or both; SIDSmonitoring; heart distress monitoring including the early detection andmitigation of myocardial infarction and cardiopulmonary arrest, asexamples; and elder care, to name a few.

In an embodiment, sensor sounds 142 may be continuously “piped” to aremote device/listener or a central monitor or both. Listening devicesmay variously include pagers, cell phones, PDAs, electronic pads ortablets and laptops or other computers to name a few. Medical staff orother remote listeners are notified by the acoustic monitoring systemaccording to flexible pre-programmed protocols to respond to thenotification so as to hear breathing sounds, voice, heart sounds orother body sounds.

FIGS. 2A-B illustrate physiological acoustic monitoring system 200embodiments each having dual channel acoustic sensors 201, 202 incommunications with a physiological monitor 205. As shown in FIG. 2A, afirst acoustic sensor 210 is utilized for deriving one or morephysiological parameters, such as respiration rate. A second acousticsensor 220 is utilized to continuously monitor body sounds. In anembodiment, the second acoustic sensor 220 has a different color orshape than the first acoustic sensor 210 so as identify the sensor as abody sound listening device rather than an acoustic sensing device fordetermining a physiological parameter. In an embodiment, the body soundsensor 220 is placed over the heart to allow the monitoring of heartsounds or for determination of heart rate. In an embodiment, the bodysound sensor 220 generates a signal that bypasses monitor digitizationand signal processing so as to allow continuous listening of theunprocessed or “raw” body sounds. In particular, the first acousticsensor 210 is neck-mounted so as to determine one or more physiologicalparameters, such as respiration rate. The second acoustic sensor 220 ischest-mounted for monaural heart sound monitoring. As shown in FIG. 2B,first and second acoustic sensors 260, 270 are mounted proximate thesame body site but with sufficient spatial separation to allow forstereo sensor reception. In this manner, the listener can more easilydistinguish and identify the source of body sounds.

FIGS. 3A-B illustrate a body sound sensor 300 having acoustic 310,interconnect (not visible) and attachment 350 assemblies. The acousticassembly 310 has an acoustic coupler 312 and a piezoelectric subassembly314. The acoustic coupler 312 generally envelops or at least partiallycovers some or all of the piezoelectric subassembly 314. Thepiezoelectric subassembly 314 includes a piezoelectric membrane and asupport frame (not visible). The piezoelectric membrane is configured tomove on the frame in response to acoustic vibrations, thereby generatingelectrical signals indicative of body sounds. The acoustic coupler 312advantageously improves the coupling between the acoustic signalmeasured at a skin site and the piezoelectric membrane. The acousticcoupler 312 includes a contact portion 316 placed against a person'sskin.

Further shown in FIGS. 3A-B, the acoustic assembly 310 communicates withthe sensor cable 340 via the interconnect assembly. In an embodiment,the interconnect assembly is a flex circuit having multiple conductorsthat are adhesively bonded to the attachment assembly 350. Theinterconnect assembly has a solder pad or other interconnect tointerface with the sensor cable 340, and the attachment assembly 350 hasa molded strain relief for the sensor cable. In an embodiment, theattachment assembly 350 is a generally circular, planar member having atop side 3511, a bottom side 352, and a center. A button 359mechanically couples the acoustic assembly 310 to the attachmentassembly center so that the acoustic assembly 310 extends from thebottom side 352. The sensor cable 340 extends from one end of theinterconnect and attachment assemblies to a sensor connector at anopposite end so as to provide communications between the sensor and amonitor, as described in further detail with respect to, below. In anembodiment, an adhesive along the bottom side 352 secures the acousticassembly 310 to a person's skin, such as at a neck, chest, back, abdomensite. A removable backing can be provided with the adhesive to protectthe adhesive surface prior to affixing to a person's skin. In otherembodiments, the attachment assembly 350 has a square, oval or oblongshape, so as to allow a uniform adhesion of the sensor to a measurementsite. In a resposable embodiment, the attachment assembly 350 orportions thereof are removably detachable and attachable to the acousticassembly 310 for disposal and replacement. The acoustic assembly 310 isreusable accordingly.

FIG. 4 illustrates sensor elements for a multi-acoustic sensorconfiguration, including a power interface 513, piezo circuits 410, 420and a piezoelectric membrane 412, 422 corresponding to each sensor heade.g. 210, 220 (FIG. 2A). The piezoelectric membrane senses vibrationsand generates a voltage in response to the vibrations, as described withrespect to the sensor of FIGS. 3A-B, above. The signal generated by thepiezoelectric membrane is communicated to the piezo circuit 410, 420,described immediately below, and transmits the signal to the monitor 205(FIG. 2A) for signal conditioning and processing. The piezo circuit 410decouples the power supply 513 and performs preliminary signalconditioning. In an embodiment, the piezo circuit 410 includes clampingdiodes to provide electrostatic discharge (ESD) protection and amid-level voltage DC offset for the piezoelectric signal to ride on, tobe superimposed on or to be added to. The piezo circuit 410 may alsohave a high pass filter to eliminate unwanted low frequencies such asbelow about 100 Hz for breath sound applications, and an op amp toprovide gain to the piezoelectric signal. The piezo circuit 410 may alsohave a low pass filter on the output of the op amp to filter outunwanted high frequencies. In an embodiment, a high pass filter is alsoprovided on the output in addition to or instead of the low pass filter.The piezo circuit may also provide impedance compensation to thepiezoelectric membrane, such as a series/parallel combination used tocontrol the signal level strength and frequency of interest that isinput to the op amp. In one embodiment, the impedance compensation isused to minimize the variation of the piezoelectric element output. Theimpedance compensation can be constructed of any combination ofresistive, capacitive and inductive elements, such as RC or RLCcircuits.

FIG. 5 illustrates a physiological acoustic monitor 500 for driving andprocessing signals from multi-acoustic sensor 401, 402 (FIG. 4). Themonitor 500 includes one or more acoustic front-ends 521, 522, ananalog-to-digital (A/D) converter 531, an audio driver 570 and a digitalsignal processor (DSP) 540. The DSP 540 can comprise a wide variety ofdata and/or signal processors capable of executing programs fordetermining physiological parameters from input data. In someembodiments, the monitor 500 also includes an optical front-end 525. Inthose embodiments, the monitor has an optical front-end 525,digital-to-analog (D/A) converters 534 and an A/D converter 535 to driveemitters and transform resulting composite analog intensity signal(s)from light sensitive detector(s) received via a sensor cable 510 intodigital data input to the DSP 540. The acoustic front-ends 521, 522 andA/D converter 531 transform analog acoustic signals from a piezoelectric410, 420 (FIG. 4) into digital data input to the DSP 540. The A/Dconverter 531 is shown as having a two-channel analog input and amultiplexed digital output to the DSP. In another embodiment, eachfront-end, communicates with a dedicated single channel A/D convertergenerating two independent digital outputs to the DSP. An acousticfront-end 521 can also feed an acoustic sensor signal 511 directly intoan audio driver 570 for direct and continuous acoustic reproduction ofthe unprocessed sensor signal by a speaker, earphones or other audiotransducer 562.

As shown in FIG. 5, the physiological acoustic monitor 500 may also havean instrument manager 550 that communicates between the DSP 540 andinput/output 560. One or more I/O devices 560 have communications withthe instrument manager 550 including displays, alarms, user I/O andinstrument communication ports. Alarms 566 may be audible or visualindicators or both. The user I/O 568 may be, as examples, keypads, touchscreens, pointing devices or voice recognition devices, to name a few.The displays 564 may be indicators, numerics or graphics for displayingone or more of various physiological parameters or acoustic data. Theinstrument manager 550 may also be capable of storing or displayinghistorical or trending data related to one or more of parameters oracoustic data.

As shown in FIG. 5, the physiological acoustic monitor 500 may also havea “push-to-talk” feature that provides a “listen on demand” capability.That is, a button 568 on the monitor is pushed or otherwise actuated soas to initiate acoustic sounds to be sent to a speaker, handheld device,or other listening device, either directly or via a network. The monitor500 may also has a “mode selector” button or switch 568 that determinesthe acoustic content provided to a listener, either local or remote.These controls may be actuated local or at a distance by a remotelistener. In an embodiment, push on demand audio occurs on an alarmcondition in lieu of or in addition to an audio alarm. Controls 568 mayinclude output filters like on a high quality stereo system so that aclinician or other user could selectively emphasize or deemphasizecertain frequencies so as to hone-in on particular body sounds orcharacteristics.

In various embodiments, the monitor 500 may be one or more processorboards installed within and communicating with a host instrument.Generally, a processor board incorporates the front-end, drivers,converters and DSP. Accordingly, the processor board derivesphysiological parameters and communicates values for those parameters tothe host instrument. Correspondingly, the host instrument incorporatesthe instrument manager and I/O devices. A processor board may also haveone or more microcontrollers (not shown) for board management,including, for example, communications of calculated parameter data andthe like to the host instrument.

Communications 569 may transmit or receive acoustic data or audiowaveforms via local area or wide area data networks or cellularnetworks. Controls may cause the audio processor to amplify, filter,shape or otherwise process audio waveforms so as to emphasize, isolate,deemphasize or otherwise modify various features of the audio waveformor spectrum. In addition, switches, such as a “push to play” button caninitiate audio output of live or recorded acoustic data. Controls mayalso initiate or direct communications.

FIG. 6 illustrates an acoustic physiological monitoring system 600embodiment having a shared or open network architecture interconnectingone or more physiological monitors 610, monitoring stations 620 and massstorage 660. This interconnection includes proximity wireless devices612 in direct wireless communication with a particular physiologicalmonitor 610; local wireless devices 632 in communications with themonitors 610 via a wireless LAN 630; and distant wired or wirelessdevices 642, 652 in communications with the monitors 610 via WAN, suchas Internet 640 or cellular networks 650. Communication devices mayinclude local and remote monitoring stations 620 and wired or wirelesscommunications and/or computing devices including cell phones, lap tops,pagers, PDAs, tablets and pads, to name a few. Physiological informationis transmitted/received directly to/from end users over LAN or WAN. Endusers such as clinicians may carry wireless devices 632 incommunications with the WLAN 630 so as to view in real-timephysiological parameters or listen to audio data and waveforms on demandor in the event of an alarm or alert.

The network server 622 in certain embodiments provides logic andmanagement tools to maintain connectivity between physiologicalmonitors, clinician notification devices and external systems, such asEMRs. The network server 622 also provides a web based interface toallow installation (provisioning) of software related to thephysiological monitoring system, adding new devices to the system,assigning notifiers to individual clinicians for alarm notification,escalation algorithms in cases where a primary caregiver does notrespond to an alarm, interfaces to provide management reporting on alarmoccurrences and internal journaling of system performance metrics suchas overall system uptime. The network server 622 in certain embodimentsalso provides a platform for advanced rules engines and signalprocessing algorithms that provide early alerts in anticipation of aclinical alarm.

As shown in FIG. 6, audio data and corresponding audio files areadvantageously stored on virtual tape 662, which provides the storageorganization of tape cartridges without the slow, bulky, physicalstorage of magnetic tape and the corresponding human-operatorintervention to physically locate and load physical cartridges into anactual tape-drive. A virtual tape controller 662 emulates standard tapecartridges and drives on modern, high capacity disk drive systems, as iswell-known in the art. Accordingly, virtual “audio tapes” appear thesame as physical tapes to applications, allowing the use of manyexisting cartridge tape storage, retrieval and archival applications.Further, while the upper-limit of a physical tape cartridge may be a fewhundred megabytes, a virtual tape server 662 can be configured toprovide considerably larger “tape” capacity. Mount-time is near-zero fora virtual tape and the data is available immediately. Also, whiletraditional physical tape systems have to read a tape from thebeginning, moving sequentially through the files on the tape, a virtualdrive can randomly access data at hard-disk speeds, providing tape I/Oat disk access speeds.

Additionally shown in FIG. 6, a sound processing firmware module ofcertain embodiments accesses a database 670 of sound signatures 660 andcompares the received signal with the entries in the database tocharacterize or identify sounds in the received signal. In anotherembodiment, the sound processing module generates and/or accesses adatabase 670 of sound signatures specific to a patient, or specific to aparticular type of patient (e.g., male/female,pediatric/adult/geriatric, etc.). Samples from a person may be recordedand used to generate the sound signatures. In some embodiments, certainsignal characteristics are used to identify particular sounds or classesof sounds. For example, in one embodiment, signal deviations ofrelatively high amplitude and or sharp slope may be identified by thesound processing module. Sounds identified in various embodiments by thesound processing module include, but are not limited to, breathing,speech, choking, swallowing, spasms such as larynx spasms, coughing,gasping, etc.

Once the sound processing module characterizes a particular type ofsound, the acoustic monitoring system can, depending on the identifiedsound, use the characterization to generate an appropriate response. Forexample, the system may alert the appropriate medical personnel tomodify treatment. In one embodiment, medical personnel may be alertedvia an audio alarm, mobile phone call or text message, or otherappropriate means. In one example scenario, the breathing of the patientcan become stressed or the patient may begin to choke due to saliva,mucosal, or other build up around an endotracheal tube. In anembodiment, the sound processing module can identify the stressedbreathing sounds indicative of such a situation and alert medicalpersonnel to the situation so that a muscle relaxant medication can begiven to alleviate the stressed breathing or choking.

According to some embodiments, acoustic sensors described herein can beused in a variety of other beneficial applications. For example, anauscultation firmware module may process a signal received by theacoustic sensor and provide an audio output indicative of internal bodysounds of the patient, such as heart sounds, breathing sounds,gastrointestinal sounds, and the like. Medical personnel may listen tothe audio output, such as by using a headset or speakers. In someembodiments the auscultation module allows medical personnel to remotelylisten for patient diagnosis, communication, etc. For example, medicalpersonnel may listen to the audio output in a different room in ahospital than the patient's room, in another building, etc. The audiooutput may be transmitted wirelessly (e.g., via Bluetooth, IEEE 802.11,over the Internet, etc.) in some embodiments such that medical personnelmay listen to the audio output from generally any location.

FIGS. 7-8 illustrate alternative breath sound generators 701, 702 forproviding an audio output for an acoustic sensor. As shown in FIG. 7A,acoustic sensor data is input to a processor board 701 so as to generatea corresponding breathing sound from a speaker or similar audiotransducer. The audio data is A/D converted 710, down-sampled 720 andcompressed 730. The monitor receives the compressed data 732,decompresses the data 740 and outputs the respiration audio 742 to aspeaker. In an embodiment, the breath sound is combined with a pulseoximeter pulse “beep.” However, unlike a pulse beep, this breath “beep”output may utilize nearly the full capacity of the processor board datachannel 732.

As shown in FIG. 7B and FIGS. 8A-C, an envelope-based breath soundgenerator advantageously provides breath sound reproduction at reduceddata rates, which will not interfere with the data channel capacity of asignal processing board. Audio data is A/D converted 710 and input to anenvelop detector 750. FIG. 8A illustrates a representative acousticbreath sound signal 810 derived by a neck sensor from tracheal air flow.The sound signal 810 has an envelope 820 with “pulses” corresponding toeither inhalation or exhalation. The envelope detector 750 generatesbreath tags 760 describing the envelope 820. These breath tags 760 aretransmitted to the monitor in lieu of the compressed audio signaldescribed with respect to FIG. 7A, above. In one embodiment, the breathtags describe an idealized envelope 830, as shown in FIG. 8B. In anotherembodiment, the breath tags also include detected envelope features 842,843, 844 that are characteristic of known acoustically-related phenomenasuch as wheezing or coughing, as examples. At the monitor end, envelopsynthesis 770 reproduces the envelope 830 (FIG. 8B) and fills theenvelope with an artificial waveform, such as white noise 780. Thisreconstructed or simulated breath signal is then output 782 to a speakeror similar device. In another embodiment, the breath tags aretransmitted over a network to a remote device, which reconstructs thebreathing waveform from the breath tags in like manner.

In various other embodiments, acoustic breathing waveforms are detectedby an acoustic sensor, processed, transmitted and played on a local orremote speaker or other audio output from actual (raw) data, syntheticdata and artificial data. Actual data may be compressed, but is a nearlycomplete or totally complete reproduction of the actual acoustic soundsat the sensor. Synthetic data may be a synthetic version of thebreathing sound with the option of the remote listener to requestadditional resolution. Artificial data may simulate an acoustic sensorsound with minimal data rate or bandwidth, but is not as clinicallyuseful as synthetic or actual data. Artificial data may, for example, bewhite noise bursts generated in sync with sensed respiration. Syntheticdata is something between actual data and artificial data, such as theacoustic envelope process described above that incorporates someinformation from the actual sensor signal. In an embodiment breathsounds are artificially hi/lo frequency shifted or hi/lo volumeamplified to distinguish inhalation/exhalation. In an embodiment, dualacoustic sensors placed along the neck are responsive to the relativetime of arrival of tracheal sounds so as to distinguish inhalation andexhalation in order to appropriately generate the hi/lo frequencyshifts.

FIG. 9 illustrates a physiological acoustic monitor 900 for out-patientapplications, including sudden infant death syndrome (SIDS) preventionand elder care. The monitor 900 has a sensor section 901 and a remotesection 902. The sensor section 901 has a sensor 910, a sensor interface920 and a communications element 930. In an embodiment, the sensor 910is an adhesive substrate integrated with a piezoelectric assembly andinterconnect cable, such as described with respect to FIGS. 3A-B, above.The sensor interface 920 provides power to and receives the sensorsignal from the sensor piezo circuit, as described with respect to FIGS.4-5, above. The wireless communications element 930 receives the sensorsignal from the sensor interface and transmits the signal to thecorresponding communications element 940 in the remote section 902,which provides an amplified sensor signal sufficient to drive a smallspeaker. In an embodiment, the communications link 960 conforms withIEEE 802.15 (Bluetooth).

A physiological acoustic monitoring system has been disclosed in detailin connection with various embodiments. These embodiments are disclosedby way of examples only and are not to limit the scope of the claimsthat follow. One of ordinary skill in art will appreciate manyvariations and modifications.

What is claimed is:
 1. A method of generating synthetic physiologicalsound responsive to a signal detected by an acoustic sensor attached toa patient, the method comprising: processing, at a patient monitor, asignal from an acoustic sensor responsive to a piezoelectric modulationof the acoustic sensor; detecting envelope features in the processedsignal responsive to a periodic physiological process; generating anidealized envelope based on the detected envelope features; comparingthe signal with sound signatures corresponding to physiological soundsstored in a first data repository; detecting a physiological event fromthe processed signal based on the comparison of the signal with thesound signatures; and generating a synthetic physiological soundcomprising a first sound corresponding to the generated idealizedenvelope and a second sound corresponding to a portion of the processedsignal with the detected physiological event.
 2. The method of claim 1,wherein the physiological sounds comprise breathing, speech, chocking,swallow, spasms, coughing, gasping, heart, and gastrointestinal sounds.3. The method of claim 1, wherein the idealized envelope is representedas breath tag.
 4. The method of claim 3, further comprising transmittingthe breath tag over a network in lieu of the processed signal.
 5. Themethod of claim 4, further comprising transmitting the portion of thesignal over the network.
 6. The method of claim 5, further comprisingcompressing the portion of the signal prior to the transmission over thenetwork.
 7. The method of claim 1, wherein the synthetic physiologicalsound is generated on a first computing system remote from thephysiological monitor.
 8. A system for generating syntheticphysiological sound responsive to a signal detected by an acousticsensor attached to a patient, the system comprising one or more hardwareprocessors configured to: process a signal from an acoustic sensorresponsive to a piezoelectric modulation of the acoustic sensor; detectenvelope features in the processed signal responsive to a periodicphysiological process; generate an idealized envelope based on thedetected envelope features; compare the signal with sound signaturescorresponding to physiological sounds stored in a first data repository;detect a physiological event from the processed signal based on thecomparison of the signal with the sound signatures; and generate asynthetic physiological sound comprising a first sound corresponding tothe generated idealized envelope and a second sound corresponding to aportion of the processed signal with the detected physiological event.9. The system of claim 8, wherein the physiological sounds comprisebreathing, speech, chocking, swallow, spasms, coughing, gasping, heart,and gastrointestinal sounds.
 10. The system of claim 8, wherein theidealized envelope is represented as breath tag.
 11. The system of claim10, wherein the one or more hardware processors are further configuredto transmit the breath tag over a network in lieu of the processedsignal.
 12. The system of claim 11, wherein the one or more hardwareprocessors are configured to transmit the portion of the signal over thenetwork.
 13. The system of claim 12, wherein the one or more hardwareprocessors are further configured to compress the portion of the signalprior to the transmission over the network.
 14. The system of claim 8,wherein the one or more hardware processors comprise a first hardwareprocessor and second hardware processor located remotely from the firsthardware processor over a network.
 15. The system of claim 14, whereinthe execution of the generation of the synthetic sound is executed bythe second hardware processor.
 16. A system for generating syntheticphysiological sound responsive to a signal detected by an acousticsensor attached to a patient, the system comprising: means forprocessing signal from an acoustic sensor responsive to a piezoelectricmodulation of the acoustic sensor; means for detecting an envelope fromthe processed signal; means for detecting a physiological event from theprocessed signal; and means for generating a synthetic physiologicalsound based on the envelope detection and detected physiological event.